Energy harvesting has grown in popularity and was just added as a subconference at the SPIE conferences. It is the ability to harness energy from radio waves or from people walking to power small devices.  In the near future we should have cell phones and iPods that partially recharge just from us carrying the devices around on our bodies.

I think this is an interesting idea to leverage the popularity of soccer as a way to displace kerosene lamps by having a soccer ball charge an internal battery while it is being kicked. There is the problem of which kid gets to use the soccer ball to power their LED lamp at night, but I think it is a great start for inspiring other ideas.

Could you do something similar with a hockey puck? Or with a frisbee that charges from spinning and being thrown and can use that power to light up at night.